@geebutbut is correct, they are using HRV during a ramp test to estimate LT1. And yes, there is some questions about it’s validity. This is a good article explaining it.
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I actually saw that recently. All of our testing protocols (ramp tests, % of 20 min TT, 5k run, etc.) are at best estimates unless we go to a lab. 
Even lab data requires good protocols and someone capable of interpreting. Per that updated view article, I do move around during workouts and have always noticed changes in breathing patterns and HR on endurance rides. For example HR sitting at 138, changing position, and then HR dropping to 130 and changes in breathing before rebounding back up to 138 after 10+ seconds. Years ago I thought it was a bad HRM, but I saw the same play out after switching from Tickr X to Garmin HRM, and then seeing agreement between Garmin HRM and Apple Watch.
And so I was not surprised after running a lot of old data thru Collab notebook to find it difficult to extract good info from HRV even on inside rides where the data is less noisy. I had a lot of inside and outside data going back 3+ years after getting a Edge 530 and turning on HRV logging.
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This is true, you don’t need many hours to burn out.
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If I’m doing Z2 on the trainer and I sit up to wipe my forehead, blow my nose, or eat a little solid food, my HR can easily go up 5-10 bpm.
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LOL mine goes down for about 10 seconds, and then back to normal. Same outside.
2 days ago, endurance ride outside:
HR dropped from 144bpm to 134bpm from sitting up and taking a bite, then back up to 142bpm. Power was fairly constant.
I’ve seen that since doing HR only spin classes in 2014.
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Ditto, the change from a lower (more prone-like) position is one influence from some study I heard of a while ago. Then the additional demand on the body to support itself once you release the bars all seem related in my experience.
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that’s exactly the same for me lol
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I definitely have seen my heart rate change based on position, eating, drinking, etc. during rides and runs. I guess I figured I needed a proxy for LT1 and dfa alpha 1 seemed as good as any other estimate. It put me in the “I can have a conversation, but the other person knows I am exercising” zone ISM has talked about. Plus, playing around with new technologies and data is just fun, which is what this should be about anyway. I am pretty confident that the heart rate I have been using is below LT1 because I can hold it for a couple hours without any drift.
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Guess I need new reading glasses.
Initially thought topic said Why Riding Mower Make You Faster.
After paging through various opinions, I think I will go mow the lawn now.
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Time to sell the push mower and buy a riding mower!
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That was an interesting thread, and video.
I’m wondering if one important part of the question is how quickly you need to be your fastest self.
“A lot of people think, ‘I only have one hour and a half to train, so I’m gonna go 100% at it’. You might see a fast but not super high improvement, but you gonna plateau. And eventually you’re going to deteriorate because you developed the glycolitic fibers very well, so that turbo looks really good, but eventually you’re not developing the other fibers”
So let’s say, you want to be as fast as possible in the next few months (2 to 6 maybe ?), then a Sweespot base training is best. If you don’t mind a slower but more long term (years ?) and eventually higher progression, then a focus on Z2 is best.
Is that a fair statement based on what ISM is saying ?
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In a TR ride I did, the instructions during the ride asked me to imagine I was in a race. My HR went up between 5-10 beats. I have tested it on other rides and days. Every time the same. I can raise the HR with up to 10 beats. Wish it would work on W too.
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Anxiety and related triggers that impact the body are real.
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I’d be careful of how you characterize ISM Z2 vs Sweetspot, ISM Z2 is ~80% of FTP (based on the discussion above) SS is ~90% of FTP so I wouldn’t call it ‘well away’. Different for sure, but maybe not night and day different.
Time constrained is different than TSS constrained. I consider myself time constrained, and as an example, I had my only available times to workout on Friday night and Saturday morning last week. I did 1hr Vo2 on Friday and 1.5hr threshold on Saturday, I wouldn’t say it was easy, but I completed every interval and rated it very hard. (I had other rides that week as well, but I’m just highlighting I can stack hard rides back to back and be able to recover adequately).
I also think you might be editorializing a bit what ISM says about required ride time for improvement. He said something along the lines of ‘even 1.5hr, 1:15 is enough to see improvement’ I don’t remember him ever mentioning 45min Z2 rides. (I could be wrong about that, but I don’t remember any talk of rides under an hour from ISM).
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“ISM Z2 is ~80% of FTP”. That’s not a statement he makes, but some numbers we made up in that thread, right ?
ISM himself in this video discards basing Z2 on a % of FTP. Preferred method : metabolic test, then by feeling (conversation test).
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Correct, from what I’ve seen, users range between mid 60% and up to low 80 percent! Also, metabolic test is best, followed by talk test. (As far as I understand).
I am sure it also depends a lot on how “realistic” the FTP is the percentage is base on. Another reason, why the percentage is pointless.
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One thing I’ve never understood, and would like to. When you say 1hr of Z5 is that a 1hr workout that has Z5 intervals in it (so maybe like 15-25 minutes spent in Z5) or does this mean 60 minutes spent in Z5 specifically?